Method and system for utilizing smart antennas in establishing a backhaul network

ABSTRACT

A method and system for utilizing smart antenna in transmission of messages between nodes are disclosed. A wireless communication system includes a plurality of nodes, and each node is capable of being connected to each other node. At least a portion of the nodes are provided with a smart antenna configured to generate a plurality of directional beams. Each node maintains a list of other nodes and beam configuration information to be used in transmission of messages to other nodes. When a source node is required to transmit to a target node, the source node retrieves the beam configuration information and transmits with a directional beam directed to the target node.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/015,557, filed Dec. 17, 2004, which claims priority from U.S.Provisional Application No. 60/578,677 filed Jun. 10, 2004, which isincorporated by reference as if fully set forth.

FIELD OF INVENTION

The present invention is related to wireless communications. Moreparticularly, the present invention is a method and system whichutilizes smart antennas in establishing a backhaul network.

BACKGROUND

One of the most important issues in a wireless communication system isto increase of capacity of the system by decreasing interference. Arrayantennas (also known as smart antennas) have been developed to improvecapacity and to reduce interference. A smart antenna uses a plurality ofantenna elements to generate a directional beam radiating signals onlytoward a particular direction in azimuth, and selectively detectssignals transmitted from a particular direction. With a smart antenna, awireless communication system is able to increase capacity and reduceinterference since signals are radiated to a narrow region in a coveragearea. This increases overall system capacity since a transmitter mayincrease the transmission power level of the directional beam withoutcausing excessive interference to other transmitters and receivers, suchas wireless transmit/receive units (WTRUs) and base stations.

A wireless communication system generally comprises a plurality ofnodes, such as base stations and radio network controllers, or the like.The nodes are typically connected to each other with wired connections,such as a mesh network or a cellular network. The nodes communicate witheach other and transmit messages, such as backhaul messages.

However, there is a disadvantage with wired connections for establishinga backhaul network in that wired connections are expensive, timeconsuming, and inflexible for modification or change of the network. Inparticular, mesh networking requires nodes to be connected with eachother. When a new node is added to the mesh network, there is a largeburden (in terms of both cost and time) for establishing new connectionsto the new node for backhauling.

Therefore, there is a need for a cost effective, less time consuming,and flexible method and system for establishing a backhaul network.

SUMMARY

The present invention is a method and system for utilizing a smartantenna in establishing a backhaul network. The present invention isdirected to using smart antennas in for improving in-cellcommunications, increasing throughput and forming at least a portion ofa flexible backhaul network for conveying backhaul data. The presentinvention is implemented in a wireless communication system whichincludes a plurality of nodes, and wherein each node is connectedtogether in a mesh network. At least a portion of the nodes are providedwith one or more smart antennas which are configured to generate aplurality of directional beams. Each node having one or more smartantennas maintains a list of other nodes having smart antennas and beamdirection and configuration information to be used in transmission ofmessages to those other nodes. When a source node is required totransmit backhaul data to a target node, the source node retrieves thebeam direction and configuration information for the target node andtransmits the messages with a directional beam directed to the targetnode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a network of a plurality of nodes inaccordance with the present invention.

FIG. 2 is a block diagram of a node made in accordance with the presentinvention.

FIG. 3 is a flow diagram of a process of utilizing smart antennas intransmission of messages between nodes in accordance with the presentinvention.

FIG. 4 is a diagram of an example of a beam pattern generated by a nodein accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is applicable to any wireless communication systemincluding, but not limited to, Time Division Duplex (TDD), FrequencyDivision Duplex (FDD), and Time Division Synchronous Code DivisionMultiple Access (TD-SCDMA), as applied to a Universal MobileTelecommunications System (UMTS), CDMA2000, CDMA in general, GlobalSystem For Mobile Communications (GSM), General Packet Radio System(GPRS), and Enhanced Data Rates For GSM Evolution (EDGE).

Hereafter, the terminology “WTRU” includes but is not limited to a userequipment, a mobile station, a fixed or mobile subscriber unit, a pager,or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “node” includesbut is not limited to a base station, a Node-B, a site controller, anaccess point or any other type of interfacing device in a wirelessenvironment.

FIG. 1 is a block diagram of a network 100 of a plurality of nodes 102a-n in accordance with the present invention. At least one of the nodes,graphically shown as 102 n, is connected to a core network 110. Theoperation of a core network of a wireless communication system is wellknown to those of skill in the art and is not central to the presentinvention. Accordingly, the core network 110 will not be explained indetail herein.

Each node 102 a-n serves one or more WTRUs (not shown) which are locatedwithin the coverage area of the nodes 102 a-n. The network 100 may be amesh network or a cellular network. In the context of the presentinvention, both mesh networks and cellular networks transmit backhaulinformation, but there is a fundamental difference. Cellular networkstypically have fixed network infrastructures and backhaul connections.These connections are typically point-to-point and they do not change.One node transmits the backhaul data to another node at another locationin the network, and to that location only.

In the case of a mesh network, the connections between nodes change, andtherefore the backhaul data may be transmitted to different nodes atdifferent times for further routing. Particularly in the case of meshnetworks, since the backhaul connection can change from time to time, itis important to be able to adjust the smart antennas so that aconnection to a different node can be achieved without creating undueinterference to other nodes.

At least a portion of the nodes 102 a-n are provided with at least onesmart antenna (as will be explained in detail hereinafter) and utilizethe smart antenna in transmission of backhaul data to other nodes 102a-n in addition to regular download transmissions to WTRUs and uploadreceipts from WTRUs. These nodes 102 a-n are capable of generating aplurality of directional beams and steering the beams to any directionin azimuth.

It is expected that the network 100 will include nodes with wiredconnections as well as those with wireless backhaul connections that usesmart antennas. Since connections established using smart antennas canbe reconfigured and directed to different nodes, they increase theflexibility of the system. However, at least one of the nodes will haveboth a wired connection to the core network 110 and wireless connectionsto other nodes in order to provide a connection between the group ofwireless nodes and the core network that is essentially wired. At leasta portion of the nodes 102 a-n may also be provided with the capabilityto transmit backhaul information over a wired or dedicated connection. Anode (shown as node 102 n) having both wired and wireless backhaulconnections, (hereinafter referred to as a hybrid node), will be theconnection to the wired core network 110. In other words, as nodestransmit backhaul information wirelessly with the help of smartantennas, this backhaul information will be routed eventually to thecore network 110 through the hybrid node 102 n. Therefore, the hybridnode 102 n can receive and send backhaul information to the nodes withwireless backhaul connections while it receives and sends backhaulinformation to the core network 110, thereby forming a bridge.

In one embodiment, a node 102 a-n has a plurality of predetermined beams109 a-h as shown in FIG. 4, and selects one among the plurality of beams109 a-h in order to direct a transmission or reception. FIG. 4 showseight beams in azimuth that may be generated by each node 102 a-n. Itshould be noted that the beams shown in FIG. 4 are provided just as anexample and any number of beams, beam patterns, or any other type ofpattern may be implemented.

In an alternative embodiment, each beam 109 a-h may be generated anddirected in real time, rather than chosen from a set of predeterminedpositions.

A node 102 a-n selects a beam 109 a-h direction, either dynamically oramong a plurality of available positions, that provides the bestperformance in terms of system capacity, data throughput, interference,or the like. Nodes 102 a-n are generally fixed in a particular location.Therefore, once a beam 109 a-h and configuration between two nodes 102a-n is set, the direction and configuration may be stored and usedthereafter without change. Each node 102 a-n may be capable of providingmore than one beam 109 a-h for connection to other nodes 102 a-n, sincethe radio environment and the traffic load may change on a long-termbasis. Therefore, each node 102 a-n monitors signals received from othernodes 102 a-n in order to determine the radio environment, anddynamically adjusts the beam direction and signal configuration tooptimize the performance of the system.

One example of the operation of the system is as follows: a firstselected node, such as node 102 a, generates a beam and steers ittowards another selected node, such as node 102 b. This can be done byadjusting the complex weights applied to the antenna array elements asis typically done with beam forming antenna arrays. At the same time,node 102 a measures the quality of the link A to node 102 b. The qualityof the link A may be measured as signal-to-noise ratio, bit or frameerror rate, or some other measurable quality indicator. The transmittingnode 102 a finds the best antenna beam direction, the best combinationof weights to maximize the link quality in this case, and stores boththe link quality measure and the corresponding beam direction (weights).The transmitting node 102 a does this for all nodes that are in thevicinity and stores the corresponding quality and beam information.

Any node 102 a-n can be flexibly and wirelessly connected ordisconnected to other nodes 102 a-n by selectively directing one or morebeams at the other nodes 102 a-n. In FIG. 1, the first node 102 atransmits messages to the second node 102 b using a directional beam A,and to a fourth node 102 d using a directional beam B. The directionalbeams A and B are independently controlled and can be transmittedsimultaneously. Since each directional beam A and B is radiated onlytoward a particular direction, it does not cause excessive interferenceto other nodes 102 a-n or WTRUs.

FIG. 2 is a block diagram of a node 202 in accordance with the presentinvention. The node 202 comprises a smart antenna 204, a controller 206,a memory 208 and an optional wired link 210. The wired link 210 may be alink to the core network 110 or to another node. The node 202 implementsa signal processing algorithm to adapt to user movement, changes in theradio-frequency environment and multipath along with co-channelinterference. A radio resource management (RRM) function implemented bythe controller 206 decides how radio resources should be allocated inthe node 202.

The smart antenna 204 comprises a plurality of antenna elements (notshown) to generate a plurality of directional beams under the control ofthe controller 206. Each beam functions as a wireless connection betweenthe node 202 and other nodes. As aforementioned, since the node 202 istypically fixed in a particular location, a beam direction andconfiguration between two nodes can be predetermined and stored in thememory 208. The memory 208 maintains a list of other nodes and beamdirection and configuration information for each of those other nodes.When the node 202 is required to transmit messages, such as backhauldata, to another node, the controller 206 retrieves corresponding beamdirection and configuration information from the memory 208 andgenerates a directional beam steered to a particular direction andtransmits the messages using the beam.

In the case of a hybrid node 102 n, this process is followed inestablishing wireless connections to other nodes with the help of thesmart antenna 204. When the hybrid node 102 n establishes a backhaulconnection to the core network 110, or another node, there is noconfiguration information or no beam selection since the wired link 210is physically fixed and will always provide a connection between thesame two nodes.

In accordance with the present invention, the smart antenna 204preferably has a multi-beam capability, in which each beam can be usedindependently. A node 202 generates more than one directional beam totransmit backhaul data to a plurality of other nodes at the same time.Since the same frequency may be reused for more than one directionalbeam in the same coverage area, the system capacity is substantiallyincreased.

Several nodes may be coupled together with several beams. This makes itconvenient to change connections and dynamically adapt to changes in theradio environment. For example, two beams may be provided for connectionbetween two nodes. If one beam suffers from excessive interference, thenthe nodes may switch to another beam for transmission of messages.

The use of smart antennas enables the formation of flexible backhaullinks between nodes. Since each node is configured to generate aplurality of directional beams and is capable of steering thedirectional beams to any direction in azimuth, when a new node is addedto the network 100, existing nodes may establish new connections to thenew node by simply setting a new beam direction and configurationdirected to the new node. In addition, when an existing node is removedfrom the network 100, nodes may simply delete beam direction andconfiguration information for the removed node from memory 208. Thepresent invention makes additional installation or removal of facilitiesunnecessary for establishing or removing connections between nodes. Itshould be noted that the present invention may be implemented either ina mesh network or in a cellular network.

One of the strengths of mesh networking is the ability to create newlinks and delete other links between nodes depending on a plurality offactors, including a traffic load, interference, and individual nodeperformance. As shown in FIG. 1, a plurality of nodes 102 a-n arecoupled to each other using smart antennas. The lines between the nodes102 a-n in FIG. 1 indicate possible links A-F. Control may becentralized, whereby at least one node functions as a controlling nodeto control the connection between nodes, or may be decentralized, wherecontrol is distributed over several nodes or all nodes. If one node isdesignated as a controlling node, the controlling node collectsinformation regarding traffic conditions and performances in each node,and determines the best traffic route for transmission of messages fromone node to another node.

Each node 102 a-n preferably transmits one or more beacon signals in itsone or more beams, which provide information useful for networkoperation. For example, the beacon signals may transmit current powerlevels, traffic levels, interference levels, and other parameters.Beacon signals may also include priority of access, security,identification, and other varying types of access control and securitycontrol information. The beacon signals are measured periodically ornon-periodically, and the parameters are utilized as the basis foradjusting connections between nodes in order to find the most efficienttraffic routes. Forming at least a portion of the backhaul connectionswirelessly by using smart antennas in accordance with the presentinvention allows flexibility and reduces unnecessary cost and time forestablishing and adjusting connections between nodes.

For example, as shown in FIG. 1, if the traffic load between the secondnode 102 b and the fourth node 102 d is too heavy, other nodes recognizethe traffic conditions between the two nodes 102 b, d by reading thebeacon signals of the nodes 102 b, d, as will be described in detailhereinafter. If the first node 102 a desires to route traffic to thefifth node 102 e, it will avoid, if possible, the second and fourthnodes 102 b, d and will alternatively route traffic through the Nth node102 n.

The present invention not only has the advantage of providing aflexible, wireless mesh network, but also the backhaul information(which is typically sent via a wired line) may now be sent via the sameflexible links through the smart antenna. Implementation of this type ofdual-use smart antenna scheme in accordance with the present inventionresults in significant advantages over current wireless communicationsystems.

FIG. 3 is a flow diagram of a process 300 of utilizing smart antennas intransmission of messages between nodes in accordance with the presentinvention. At least a portion of the nodes are provided with at leastone smart antenna, which is configured to generate a plurality ofdirectional beams and to steer then independently in azimuth (step 302).Each beam is used as a wireless connection to other nodes in addition toregular traffic of downloads to WTRUs and uploads from WTRUs. Each nodemaintains a list of other nodes and beam direction and configurationinformation to be used for transmission to the other nodes (step 304).It should be noted that steps 302 and 304 are typically performed uponsetting up a system or reconfiguring the system to accept or deletenodes, and will not typically have to be formed during normal operation.When a source node is required to transmit to a target node, the sourcenode retrieves beam direction and configuration information for thetarget node from the memory, and generates a directional beam using thebeam direction and configuration information (step 306). Once a node isselected for transmission of backhaul data, based on link quality andother considerations such as traffic density, the transmitting nodeselects the beam direction (weights) from the list and applies it to theantennas.

The process for measuring the quality of links and storing relevantinformation may need to be done periodically since the environment maychange and adjustment of beam directions may be necessary. The sourcenode then transmits to the target node with the generated directionalbeam (step 308).

In an optional step, a change in the network may occur whereby a newnode may be added to the network, an existing node may be removed fromthe network, or radio frequency or other conditions may change. Inresponse to the change, other nodes update the list of beam directionand configuration information to reflect the change (step 310).

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

1. A wireless communication system for utilizing at least one smartantenna for establishing a backhaul network, the system comprising: aplurality of nodes, each node connected to at least one neighbor node,each node comprising: a smart antenna configured to generate a pluralityof directional beams; a memory configured to store a list of neighbornodes having connections and beam configuration information to be usedin transmission of messages to the neighbor nodes; and a controllerconfigured to select a particular directional beam for transmitting aparticular message to another node; at least one of the nodes being ahybrid node that further comprises a wired backhaul connection to a corenetwork.
 2. The system of claim 1 wherein the hybrid node of claim 1further comprises a wired backhaul connection to at least neighbor node.3. The system of claim 1 wherein the generated plurality of directionalbeams are selected from a set of predetermined positions.
 4. The systemof claim 1 wherein the generated plurality of directional beams aredynamically selected and directed in real time.
 5. The system of claim 5wherein the directional beams are configured to provide the bestperformance in terms of system capacity, data throughput, andinterference.
 6. The system of claim 1 wherein at least a portion of thenodes are configured to transmit backhaul information over the wiredbackhaul connection.
 7. The system of claim 1 wherein the hybrid node isconfigured to receive and transmit backhaul information to another nodewith a wireless backhaul connection while the hybrid node receives andtransmits backhaul information to the core network.
 8. The system ofclaim 1 wherein the plurality of nodes comprise a mesh network.
 9. Thesystem of claim 1 wherein the plurality of nodes comprise a cellularnetwork.
 10. A wireless communication node for use in a wirelesscommunication system comprising: a smart antenna configured to generatea plurality of directional beams; a memory configured to store a list ofneighbor nodes and beam configuration information to be used intransmission of messages to the neighbor nodes; and a controllerconfigured to select a particular directional beam for transmitting aparticular message to another node for establishing a backhaul network.11. The wireless communication node of claim 8 further comprising awired backhaul connection to a core network.
 12. The wirelesscommunication node of claim 11 wherein the node is configured to receiveand transmit backhaul information to another node with a wirelessbackhaul connection while the node receives and transmits backhaulinformation to the core network.
 13. The wireless communication node ofclaim 8 further comprising a wired backhaul connection to at least oneother node.
 14. The wireless communication node of claim 8 wherein thegenerated plurality of directional beams are selected from a set ofpredetermined positions.
 15. The wireless communication node of claim 8wherein the generated plurality of directional beams are dynamicallyselected and directed in real time.
 16. The wireless communication nodeof claim 15 wherein the directional beams are selected to provide thebest performance in terms of system capacity, data throughput, andinterference.
 17. The wireless communication node of claim 8 wherein thenode is configured to transmit backhaul information over the wiredbackhaul connection.
 18. The wireless communication node of claim 8configured for use in a wireless mesh network.
 19. The wirelesscommunication node of claim 8 configured for use in a cellular network.